Contact probe

Abstract

A contact probe consisting of a tubular receptacle, a needle member received in the tubular receptacle in a freely slidable manner, and a compression coil spring coiled around the needle member, and compressed between a shoulder surface defined in the receptacle and another shoulder surface defined in the needle member to urge the needle member out of the front end of the tubular receptacle. The compression coil spring is provided with a large diameter portion at its inner end for elastically engaging with an inner surface of the receptacle so that the needle member may be replaced without requiring the receptacle to be removed.

What we claim is: 
     
       1. A contact probe, comprising: a tubular receptacle having an inner surface defining an inner diameter, a front end, and a rear end, said tubular receptacle including a first shoulder surface at one end thereof;   a needle member slideably received in said tubular receptacle, said needle member including a second shoulder surface at one end thereof;   a compression coil spring coiled around said needle member, the ends of said coil spring respectively abutting said first and second shoulder surfaces, whereby said needle member is urged out of said front end of said tubular receptacle; and   means for limiting an extent of movement of said needle member out of said front end of said tubular receptacle;   said compression coil spring including a large diameter portion adjacent said first shoulder surface, said large diameter portion adapted to frictionally engage said inner surface of said receptacle, the remainder of said compression coil spring having an outer diameter generally smaller than said inner diameter of said receptacle.   
     
     
       2. A contact probe according to claim 1, wherein said means for limiting an extent of the movement of said needle member out of said front end of said tubular receptacle comprises a wire coil securely wrapped around said needle member and having an end which can abut said one end of said compression coil spring. 
     
     
       3. A contact probe according to claim 2, wherein said wire coil extends across said rear end of said receptacle over an entire stroke of said needle member in said receptacle. 
     
     
       4. A contact probe according to claim 3, wherein said wire coil comprises a coarsely wound portion, a finely wound portion, and a bonding agent applied to said coarsely wound portion of said wire coil. 
     
     
       5. A contact probe according to claim 2, wherein said needle member, and said compression coil spring form a needle member assembly which can be inserted into said receptacle in one body for assembly and maintenance purposes, said compression coil springs being engaged between said wire coil and said front end of said needle member before said needle member assembly is inserted into said receptacle. 
     
     
       6. A contact probe according to claim 1, wherein said shoulder surface of said receptacle consists of an annular bead projecting radially and inwardly from said receptacle. 
     
     
       7. A contact probe according to claim 1, wherein said shoulder surface of said needle member is defined by a sleeve fitted onto said needle member. 
     
     
       8. A contact probe according to claim 3, wherein said needle member comprises a continuous core conductor extending from a front end of said needle member at least a certain distance from a rear end of said receptacle. 
     
     
       9. A contact probe according to claim 8, wherein said core conductor is covered by an insulating layer substantially over an entire surface of a part of said core conductor which can be located in said receptacle. 
     
     
       10. A contact probe according to claim 3, further comprising a lead wire led out of the rear end of said receptacle and connected to the rear end of said needle member via connector means. 
     
     
       11. A contact probe according to claim 10, wherein said means for limiting an extent of the movement of said needle member out of said front end of said tubular receptacle comprises a rear end portion of said needle member having an enlarged diameter which can abut said one end of said compression coil spring. 
     
     
       12. A contact probe according to claim 11, wherein said needle member, said compression coil spring, and said lead wire form a needle member assembly which can be inserted into said receptacle in one body for assembly and maintenance purposes, said compression coil spring being engaged between said rear end and said front end of said needle member before said needle member assembly is inserted into said receptacle. 
     
     
       13. A contact probe, comprising: tubular receptacle having an inner surface defining an inner diameter, a front end and a rear end, said tubular receptacle including a first shoulder surface at one end thereof;   a needle member slideably received in said tubular receptacle, said needle member including a second shoulder surface at one end thereof;   a compression coil spring coiled around said needle member, the ends of said coil spring respectively abutting said first and second shoulder surface, whereby said needle member is urged out of said front end of said tubular receptacle;   said compression coil spring provided with a large diameter portion adjacent said first shoulder surface, said large diameter portion adapted to frictionally engage with said inner surface of said receptacle, the remainder of said compression coil spring having an outer diameter generally smaller than said inner diameter of said receptacle; and   a wire coil securely wrapped around said needle member, said wire coil having an end adapted to abut said large diameter portion of said compression coil spring, said wire coil limiting an extent of movement of said needle member out of said front end under the spring force of said compression coil spring.